This project is a long-term effort aimed at clarifying the evolutionary relationships within the genus Anopheles, the vectors of human malaria. Past progress has included the clarification of the evolutionary status of the species of the North American Maculipennis complex, the mapping of the salivary gland chromosomes of about 30 American and Asiatic species, the discovery that chromosomal banding patterns are subgeneric in nature and that sibling species, although morphologically identical, can be identified by means of the banding patterns of the salivary gland chromosomes. A second line of research will continue the work on enzyme polymorphism in native populations of Anopheles. Using starch gel electrophoresis, it has been possible to identify and map esterases and other enzymes, identify homozygotes and estimate polymorphism in natural populations. Major efforts will concentrate in species and in species groups with known polymorphism and extensive distribution. An immediate specific objective will be to distinguish vector from nonvector populations by means of salivary gland chromosome inversions. In Venezuela and Colombia isolated populations of Anopheles nuneztovari south and west of Lake Maracaibo are evidently responsible for elevated rates of malaria transmission, although this species is normally considered to be a nonvector in the rest of its extensive range which includes Venezuela, Colombia and the entire Amazon basin in Brazil. The vector population in Venezuela and Colombia differ by an X-chromosome inversion from all other (nonvector) populations. Last year we were able to confirm dramatically this result: in areas in which local outbreaks of malaria were occurring, and in which nuneztovari was abundant, the local populations of nuneztovari had the inverted X (Venezuelan type) chromosome.